I've followed this thread with some interest ... as JB said, we've
discussed this topic trekking back and forth from many contests in the
van.
The advent of affordable molded models has done more to cause line
problems than any other single facet of our chosen sport. Today's
molded sailplanes are so strong that they can easily part 200# test
winch line, almost at will. This is the primary reason we in the OVSS
and AMA/LSF Nats have moved to the 290# test lines we use today. If
there are no burns, abrasions, crappy knots, etc. it's unlikely that
you will be able to break the line on purpose without damaging the
model.
With aircraft of this magnitude of strength, the need for developing
good winch technique has fallen by the wayside. In my early days in
the sport, everyone flew open framework gasbags and a full pedal launch
on our SIX volt winches would result in a Monokoted bag full of sticks.
You learned to temper your foot or you learned to rebuild - fast!
Today's competition pilot doesn't need to develop any such technique,
he can simply hook up, step on the pedal and GO! Poor winch technique
is easy to spot, the smoke coming from the winch armature and excessive
wing flex are sure indicators. Moderating the amount of energy in the
line, motor and wings are all a part of launching technique that is all
too lacking among many competition pilots who have skipped the early
learning curves of winching built-up, more fragile models.
Examination of the line break often yields the answer to why the line
parted, the aforementioned abrasions, poor knots, frozen turnaround
pulleys ... equipment failures should result in a relight. The pilot
that breaks the line as they push over into the zoom has no call for a
relight, he got 90+% of the way up. The pilot who full pedal launches
through a thermal on tow shouldn't get a relight, either, unless the
equipment failed (and if he had proper technique, the line likely would
have stayed intact).
Weak links ... tried in F3B a decade or more ago, the weak link was
dropped quickly because the relative weakness of the link was actually
seen to be a safety hazard as most links failed just out of the
launcher's hand. Yes, the (rather large) relative difference between
the line and the link had much to do with the problem, but what is the
right differential? For a 100" RES or NOS vs a 3.9 meter Sharon?
Do we need devices on the winches to set torque or tension limits?
Same issue as the weak link ... what's the right amount of torque and
is it the same for every model?
A seasoned pilot acting as the Launch Master can readily evaluate each
launch and come to a likely first approximation as to cause for line
failure on the spot ... subsequent investigation at the point of
failure serves to validate whether the call was correct or not. I
would guess that the Launch Master is going to be right the majority of
the time.
Reserve one or two winches on the line for relights ... pilot calls the
break, Launch Master either denies the relight request and the pilot
continues the flight or confirms the relight and the pilot comes down
IMMEDIATELY for relaunch. If the number of breaks exceeds the number
of backup winches, call the group down and start over. I suggest if
that many lines break in the same round there are either equipment
issues or you're winching over desert scrub or through rose bushes.
Rather than look for a technological silver bullet, I propose that we,
as a part of bringing newer flyers into the competition circuit, teach
winch technique alongside air reading skills and spot landing practice.
It will improve the quality of the pilots, it will improve equipment
life, and it will allow more flying, which is really the whole point,
isn't it?
IMHO,
Tom Kallevang
Wheeling, IL
LSF President & Webmaster
LSF #303 Level V #103
AMA L292
SOAR (Chicago)
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